Modern humans (Homo sapiens) originated in eastern Africa, but they expanded at the expense of Neanderthals and other ancient hominid populations. What was the reason for their global colonization? Recent data from the area surrounding Africa's Lake Victoria (the largest tropical lake in the world) suggest that the study of volcanic eruptions, climate change, and technological innovation may reveal what fueled human dispersals westward across the tropical African continent some 50,000 years ago.